The stator end windings of many of today's turbine generators are generally insulated with a semi-conductive compound, such as CORONOX.RTM. which comprises silicon carbide and varnish. Selected surfaces of stator coils are typically painted with CORONOX.RTM. to suppress Corona activity, the art recognized term for electrical discharge from the sides of the coils associated with high voltage gradients. A CORONOX.RTM. protected winding exhibits a surface which is chalk-like, and generally deficient in mechanical and bonding properties. Moreover, leaching of this compound due to component motion and oil can contribute to poor bracing within the winding.
In the late 1960's and early 1970's, the CORONOX.RTM. layer was protected by a layer of MYLAR.RTM. and glass tape which provided only nominal physical properties.
In the late 1970's, layers of SCOTCHPLY.RTM. were applied successfully to the larger inner-cooled coils of the abovementioned generators. These layers were applied in a semi-cured state which was often characterized as being tacky to the touch. After wrapping the stator coils with this material, the assembly was heated to about 150.degree. C. for about 10 to 20 hours. The curing temperatures used for this procedure presented a constant threat of distorting copper coils, especially those currently in service. In addition, SCOTCHPLY.RTM. increased the scuff and wear resistance of the coils, yet, resulted in a slippery surface which did not bond sufficiently to other components, such as the "diamond spacers" used to separate the individual coils of the stator. Thus, a sanding procedure was instituted to prepare these surfaces to effect a good bond.
Accordingly, a need exists for an improved stator coil bracing assembly, especially for older in-service windings not protected with SCOTCHPLY.RTM. which is resistant to CORONOX.RTM. leaching. There is also a need for a sealing technique that permits better bonding between the stator coils and diamond spacers, without heating the stator coils to 150.degree. C.